The cap on carbon laid out in the Senate energy bill is the same as that contained in the bill passed by the House of Representatives in June 2009. It aims to reduce economy-wide greenhouse gas emissions by 17% of 2005 levels by 2020, 42% by 2030 and 83% by 2050. This will be implemented via a carbon cap-and-trade system that could eventually be worth as much as $2 trillion, according to likely regulator the Commodity Futures Trading Commission.

The Senate legislation aims to establish a stable